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    Optimization of parameters for the friction stir processing and welding of aa1050 aluminum alloy

    , Article Iranian Journal of Materials Science and Engineering ; Volume 18, Issue 2 , 2021 ; 17350808 (ISSN) Alishavandi, M ; Ebadi, M ; Kokabi, A. H ; Sharif University of Technology
    Iran University of Science and Technology  2021
    Friction-Stir Processing (FSP) was applied on AA1050 Aluminum Alloy (AA) to find the highest mechanical properties among 28 combinations of the rotational and traverse speed (800-2000 rpm and 50-200 mm.min-1) and four different tool probe shapes (threaded, columnar, square and triangle). To this aim, the AA standard sheet went through a single pass of FSP. The 1600 rpm and 100 mm.min-1 with threaded tool probe was chosen as the best combination of rotational and traverse speed. Grain size at the Stirred Zone (SZ) was studied using Optical Microscopy (OM). The results showed that the SZ’s grain size was refined from 30 μm down to about 12 μm due to dynamic recrystallization during FSP. The... 

    Anodizing of titanium in NaOH solution and its corrosion resistance in PBS physiologic solution

    , Article Scientia Iranica ; Volume 10, Issue 3 , 2003 , Pages 361-366 ; 10263098 (ISSN) Afshar, A ; Vaezi, M. R ; Sharif University of Technology
    Sharif University of Technology  2003
    Titanium is a highly reactive metal with an inclination to compose with oxygen. In order to increase its corrosion resistance and application, therefore, a thin layer of titanium oxide is produced on the surface by chemical and electrochemical methods. In the present research, titanium has been anodized in 20 M of NaOH solution under potentiostatic conditions at constant voltages of 25 and 35 V. The microstructure of the anodic layers has been studied by the use of a Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD). The results indicated that the structure of the anodic layers is amorphous with low porosity and that thickness increases with an increase in anodizing voltage. The... 

    Wear and friction characteristics of electrodeposited graphite-bronze composite coatings

    , Article Surface and Coatings Technology ; Volume 190, Issue 1 , 2005 , Pages 32-38 ; 02578972 (ISSN) Ghorbani, M ; Mazaheri, M ; Afshar, A ; Sharif University of Technology
    The wear and friction properties of G-Cu (Sn) composite coatings containing different amounts of graphite particles were examined. The presence of graphite particles improved antifriction properties of composite coatings. The effects of graphite percent in composite coating, tin content of matrix, load, speed and distance on the coefficient of friction and wear resistance of bronze-graphite composite coatings were studied. The results of the present studies revealed that hardness, wear resistance, coefficient of friction are dependent on volume percentage of graphite in composite coating. It was shown that the composite coating containing approximately 5.4 (vol.%) graphite and matrix with... 

    Effect of current frequency on coating properties formed on aluminised steel by plasma electrolytic oxidation

    , Article Surface Engineering ; Vol. 30, issue. 3 , 2014 , pp. 224-228 ; ISSN: 02670844 Jafarniya Kharanagh, V ; Faghihi Sani, M. A ; Rafizadeh, E ; Sharif University of Technology
    In the present study, plasma electrolytic oxidation process was carried out on aluminised steel with a pulsed bipolar electrical source at different frequencies, namely, 50, 300, 600 and 1500 Hz with constant 50% duty cycle for 10 min in an alkaline silicate electrolyte. Morphology, wear behaviour and corrosion resistance of the coatings were investigated by scanning electron microscopy, pin on disc and potentiodynamic polarisation experiment in 3·5 wt-%NaCl solution. The results showed that with increasing the pulse frequency, the density of the residual pores increases, but their size as well as the coating thickness decreases. The corrosion current density of the coating processed at 1500... 

    Optimal experiment design for plasma thermal spray parameters at bending loads

    , Article International Journal of Surface Science and Engineering ; Volume 6, Issue 1-2 , 2012 , Pages 3-14 ; 1749785X (ISSN) Azadi, M ; Moridi, A ; Farrahi, G. H ; Sharif University of Technology
    Ceramic thermal barrier coatings are applied on gas turbines and diesel engine components to protect metals from heat and this enhances the service lifetime by means of a reduction in working temperature. In the present paper, optimisation of plasma thermal spray parameters, including feed rate and nozzle distance from the specimen surface is performed by using the design of experiment method. Due to factorial approach, by considering two parameters with three variation levels, nine experiments of bending test are needed. The base material is cast aluminium alloy, A356.0-T7. The coating layers consist of a bond coat, Ni-Cr-Al-Y with a thickness of 150 μm and a top coat, ZrO2-8wt%Y2O3 with a... 

    Comparison of isothermal with cyclic oxidation behavior of “Cr-Aluminide” coating on inconel 738LC at 900 °C

    , Article Oxidation of Metals ; Volume 87, Issue 1-2 , 2017 , Pages 57-74 ; 0030770X (ISSN) Salehi Doolabi, M ; Ghasemi, B ; Sadrnezhaad, S. K ; Feizabadi, A ; HabibollahZadeh, A ; Salehi Doolabi, D ; AsadiZarch, M ; Sharif University of Technology
    Springer New York LLC  2017
    A two-step pack cementation technique was used to cover nickel-based IN-738LC superalloy with a Cr-aluminide coating layer. The IN-738LC/Cr-aluminide samples were oxidized at 900 °C for 350 and 700 h, isothermally, and 175 and 350 h, cyclically. Each cycle lasted for 25 h. Effects of the isothermal and the cyclic oxidation on (a) morphology, (b) new-phase formation, (c) weight gain, and (d) oxidation reactions were investigated by scanning electron microscopy, electron dispersive spectroscopy, X-ray diffraction, and weight gain measurements. From results, it was concluded that the oxygen attack was more severe during the cyclic oxidation than the isothermal procedure. Kinetics of the... 

    Electrodeposition of graphite-bronze composite coatings and study of electroplating characteristics

    , Article Surface and Coatings Technology ; Volume 187, Issue 2-3 , 2004 , Pages 293-299 ; 02578972 (ISSN) Afshar, A ; Ghorbani, M ; Mazaheri, M ; Sharif University of Technology
    The aim of this research is to obtain composite coatings of bronze (90% Cu-10% Sn) with graphite particles. The electrodeposition of G-Cu (Sn) composites from an alkaline bath containing cyanide is described. Composite coatings consisting of graphite particles and copper-tin were prepared by means of the conventional electrocodeposition (CECD) and sediment codeposition (SCD) techniques. The graphite particles involved were less than 10 μm. The dependence of graphite amount in the composite coatings was investigated in relation to the graphite concentration in bath, cathode current density, stir rate and technique type and it was shown that these parameters strongly affected the volume... 

    Percolation of cadmium across a mercury film

    , Article Materials Chemistry and Physics ; Volume 78, Issue 3 , 2003 , Pages 796-799 ; 02540584 (ISSN) Malek, K ; Gobal, F ; Sharif University of Technology
    Electrodeposition/dissolution of cadmium onto a film of mercury shows some deviations from the natural liquidity of mercury caused by the reduction of Cd onto it. Percolation and fractal analyzes were done on the surface and the bulk of the mercury film during diffusion of Cd species (atoms). These show that the fractal dimensions of the Cd-inserted mercury film are about 2.11 and 2.54 near the surface of the mercury film and at deeper points inside the film, respectively. The insertion process has a negligible effect on the surface morphology of the mercury film and there is a phase transition in the bulk, as well as a geometrical transition during the Cd-insertion (de-insertion) process.... 

    Electrodeposition of graphite-brass composite coatings and characterization of the tribological properties

    , Article Surface and Coatings Technology ; Volume 148, Issue 1 , 2001 , Pages 71-76 ; 02578972 (ISSN) Ghorbani, M ; Mazaheri, M ; Khangholi, K ; Kharazi, Y ; Sharif University of Technology
    Co-deposition of Cu(Zn) and graphite powders with size less than 10 μ was studied. Electrocomposite coatings were prepared by means of the conventional electrodeposition (CECD) and the sediment co-deposition (SCD) techniques. Brass electroplating cyanide bath has been selected out of electrodeposition brass. The effect of parameters such as rate of agitation and current density on the composition of electrodeposition brass and also the effect of the concentration of graphite particles in brass bath, air agitation rate on graphite incorporation within brass matrix and deposition efficiency were studied. The wear and friction properties of G-Cu(Zn) composite coatings containing different... 

    The Corrosion Behavior of Zinc and SiO2 Composite Coating

    , M.Sc. Thesis Sharif University of Technology Salehi, Farshad (Author) ; Ghorbani, Mohammad (Supervisor)
    Main aim of this work was to obtain the harder zinc coating and increasing the anti corrosive properties by mean of adding SiO2 particles by electrophoretic method.
    The coating was applied on the substrate surface by mean of electro co-deposition technique in three different electrolytes ethanol, methanol and water. The morphology of the coating in each electrolyte studied by scanning electron microscope (SEM).For the Zn/SiO2 coatings achieved in ethanol solvent the polarization and EIS tests was took place and found that for the Zn/SiO2 coating contain less than 10% SiO2 the corrosion rate decreased but for the coatings contains more than 10% SiO2 the paradox occurred because of the... 

    Synthesis of Anti-reflection and Self-cleaning Coating on Glass Substrate Using Sol-gel Method

    , M.Sc. Thesis Sharif University of Technology Sharifi Rad, Alireza (Author) ; Afshar, Abdollah (Supervisor)
    Using of solar spectrum because of its potential for producing green energy is the topic of interest in Current decade. The goal of current research is increment of efficiency by using of a single layer and double layer semiconductor TiO2 – ZnO coating that has been synthesized by sol-gel process, which have anti-reflation and self-cleaning properties that in short time and long time for durability of solar systems can be useful. In first step of this research the single layer TiO2 (by 85nm thickness, measured by FE-SEM) and ZnO (by 65nm thickness) coating with different concentrations of pore forming agents ( plironic f127 for TiO2 and CTAB for ZnO) in coating sol examined and observed... 

    Electrophoretic deposition of porous hydroxyapatite coatings using polytetrafluoroethylene particles as templates

    , Article Materials Science and Engineering C ; Volume 27, Issue 5-8 SPEC. ISS , 2007 , Pages 1482-1486 ; 09284931 (ISSN) Yousefpour, M ; Afshar, A ; Chen, J ; Zhang, X ; Sharif University of Technology
    The formation of macroporous bioactive hydroxyapatite(HA) coatings using polytetrafluoroethylene(PTFE) particles were studied. The porous HA coatings were prepared onto a pure titanium substrate by electrophoretic deposition(EPD) at 120 V for 1.5 min using ethanol suspensions mixture of HA (500 nm in size) and PTFE (1-3 μm in size) particles. Subsequently, the composite coatings obtained by EPD were heated at 900 °C for 60 min to disintegrate the organic PTFE particles and sinter the inorganic HA particles. The calcinations of the PTFE led to the formation of porosity in the HA coating. These results demonstrate a new method for creating porous HA coatings on titanium. © 2006 Elsevier B.V.... 

    Enhanced hardness and corrosion resistance of Zn/SiO2 films by electrodeposition

    , Article Journal of the Electrochemical Society ; Volume 162, Issue 9 , 2015 , Pages D480-D485 ; 00134651 (ISSN) Ghorbani, M ; Salehi, F ; Razavizadeh, O ; Sharif University of Technology
    Electrochemical Society Inc  2015
    The electrodeposition of Zn-SiO2 nanocomposites has been investigated with different electrolytes: triethanolamine as a dispersing agent, and cetyl trimethylammonium bromide and dodecyl dimethylamine oxide as ionic (cationic) and non-ionic surfactants. Appropriate electrophoretic potentials for each solution were obtained using cyclic voltammetry. The results show that the most stable SiO2 nanoparticles with zeta potential range of 25 to 41 mV, along with highest SiO2 mobility of 0.4 to 0.7 m2/V.s were dispersed by triethanolamine in ethanol and the resulting coating adhesion improved up to 5.87 MPa in the standard pull off test, with the enhanced hardness of... 

    Productivity enhancement of solar stills by nano-coating of condensing surface

    , Article Desalination ; Volume 454 , 2019 , Pages 1-9 ; 00119164 (ISSN) Zanganeh, P ; Soltani Goharrizi, A ; Ayatollahi, S ; Feilizadeh, M ; Sharif University of Technology
    Elsevier B.V  2019
    Wettability is one of the most important factors which significantly influences solar still efficiency. Moreover, it determines the condensation mode, i.e., filmwise or dropwise condensation. In the present study, materials with different wettability were applied as the condensing surface to evaluate the effect of wettability on the distillate production of a single slope solar still. To compare the effects of dropwise and filmwise condensation on the condensate yield, the wettability of the condensing surface was changed by applying a nano-silicon solution according to a dip coating technique. All the experiments were conducted at three surface inclination angles. The results revealed that... 

    Evaluation of hot corrosion behavior of plasma sprayed thermal barrier coatings with graded intermediate layer and double ceramic top layer

    , Article Surface and Coatings Technology ; Volume 288 , 2016 , Pages 36-45 ; 02578972 (ISSN) Pakseresht, A. H ; Javadi, A. H ; Ghasali, E ; Shahbazkhan, A ; Shakhesi, S ; Sharif University of Technology
    Elsevier  2016
    In the present work, the hot corrosion behavior of two types of multilayer plasma sprayed TBC were investigated and compared with functionally graded and conventional TBCs. These kinds of multilayer coatings consisted of nano/μ alumina as a top coat on YSZ layer, a metallic bond coat and a functionally graded intermediate layer deposited between YSZ and bond coat layers. All the layers were sprayed on the Ni-base super alloy substrate. The hot corrosion resistance of the plasma sprayed coatings was examined at 1050 °C for 40 h, using a fused mixture of 45 wt% Na2SO4 + 55wt%V2O5. Before and after hot corrosion, the microstructure and phase analysis of the coating were studied using scanning... 

    A simple route to synthesize zirconia antistatic thin films on glass substrates and their application to polymer-based composites

    , Article Materials Chemistry and Physics ; Volume 244 , 1 April , 2020 Naderi, A ; Dolati, A ; Afshar, A ; Palardy, G ; Sharif University of Technology
    Elsevier Ltd  2020
    In this study, zirconia antistatic coatings were synthesized by a simple dip coating sol-gel route on glass substrates, then applied to polymer-based composites to potentially improve their dust or water repellent capabilities. The coating solution contained a precursor (ZrCl4), solvent (isopropanol) and coupling agent. FTIR spectra confirmed ZrO2 and ZrO compounds in both solution and antistatic coating. FE-SEM images indicated ZrO2 fibers’ thickness was controlled by changing ZrCl4 concentration (150 g–15 g ZrCl4/l) or relative humidity (20%–60%) during coating drying. Fibers grew thicker when decreasing the former or increasing the latter. The surface electrical resistivity for all... 

    Synthesis and Characterization of Anticorrosive Hybrid Epoxy Coating based on Polyaniline/Nanodiamond Nanostructures

    , M.Sc. Thesis Sharif University of Technology Mohammadkhani, Rahman (Author) ; Shojaei, Akbar (Supervisor) ; Pirhady, Nahid (Co-Advisor)
    One of the ways that corrosion control is presented is the use of coatings that have good properties such as high adhesion, impact resistance, ultraviolet radiation, and so on. They also have other unique properties like anti-corrosion property. To achieve coatings with these advanced properties, they use special properties of nanocomposites. Nanocomposites can add or improve one or more properties to coating properties.In the present study, we tried to first synthesize NanoDiamond/Polyaniline hybrid nanoparticles in different percentages and then use this hybrid in epoxy ester coating. To characterize this hybrid, various analyzes such as FE-SEM, TEM, FT-IR, UV-Visible, TGA and XRD were... 

    Electrochemical Deposition of Zinc/Nickel Multilayer Coating and Investigating the Effect of Morphology and Phase Structure on the Dissolution of Zinc/Nickel Alloy Coating

    , M.Sc. Thesis Sharif University of Technology Tahmasebi, Maedeh (Author) ; Ghorbani, Mohammad (Supervisor)
    The multilayer coating (Zn-Ni)1/(Zn-Ni)2 is deposited from a single bath with a zincate-sulfate compound and by changing the current density. The effect of current density and the number of layers on the chemical composition, surface morphology, roughness, phase structure, and corrosion resistance of multilayer coatings respectively using atomic absorption spectroscopy, FE-SEM microscope, roughness tests, X-ray analysis, and electrochemical techniques such as Tafel polarization and impedance was investigated and compared with single-layer coatings. Because the amount of nickel in the composition of the coatings is less than 27%, in all the studied currents, the deposition is anomalous. The... 

    Synthesis and Investigation of Properties of Intumescent Fireproofing Paint with Oxide Nanoparticles

    , M.Sc. Thesis Sharif University of Technology Hasannezhad, Asghar (Author) ; Dolati, Abolghasem (Supervisor)
    Intumescent paints are coatings designed for passive fire protection of steel and other materials. In this research, the performance of water-based intumescent coating with vinyl acetate resin for cellulose fire conditions and epoxy-based coatings for hydrocarbon fire conditions has been investigated. The fire resistance of coatings was evaluated according to the ASTM E119 standard for water-based coating and UL1709 standard for epoxy-based intumescent coating. For the water-based intumescent coating, the expansion of char was investigated in a furnace with a temperature of 800°C for 1 hour. Thermal decomposition was studied by thermogravimetric analysis (TGA). Also, flammability was... 

    Influence of aluminide diffusion coating on the tensile properties of the Ni-base superalloy René 80

    , Article Surface and Coatings Technology ; Volume 202, Issue 8 , 2008 , Pages 1385-1391 ; 02578972 (ISSN) Rahmani, Kh ; Nategh, S ; Sharif University of Technology
    Ni-base superalloy René 80 is widely used in manufacturing aircraft turbine blades. The service temperature of this alloy is in the range of 760-982 °C. Although this alloy possesses suitable mechanical, oxidation and hot corrosion properties, it is coated in order to increase its wear, oxidation, erosion and hot corrosion properties against harmful environmental service conditions. In this paper the influence of applying diffusion coating (CODEP-B) on the tensile properties of René 80 has been studied in the temperature range of 22-982 °C. Experimental results show that the tensile properties of the coated specimens are relatively lower than that of uncoated ones in the same conditions. But...